In Beijing, yesterday, the smog and a looming thunderstorm combined to generate darkness at noon, an eerie visual effect on what is a strange day every year, the anniversary of the crackdown on pro-democracy protesters on June 4th, 1989, which killed hundreds, possibly more.

Yesterday, the vast square at the heart of Beijing was full of camera-toting tourists, as two large screens beamed images of a thriving China to tourists. Most of the visitors on Tiananmen Square were facing away from the area where the tanks rolled in 24 years ago to violently disperse the pro-democracy protesters who had camped out for weeks on the vast concourse.

They were looking towards the giant portrait of Mao Zedong, the Great Helmsman, which sits on the front of the Forbidden City. In 1989, during the student-led protests, the portrait had a paint bomb thrown at it, but yesterday the painting was pristine. There was a fairly heavy presence around the square, but there generally is as this is the heart of Beijing, close to the seat of power and a hugely symbolic area for the Communist leadership. I saw two Swat teams, and the kung fu plain-clothed police seem more discreet this year than they were, say, four years ago, for the 20th anniversary. Back then anyone entering Tiananmen Square went through security checks and the atmosphere was heavy.

China is a richer, freer place than it was in 1989, but it is still a country that has not come to terms with what happened that day. Today. Tomorrow. That year. That day. Special day. Massacre. Big yellow duck. All of these words are banned on China’s version of the banned Twitter-like service, Weibo, along with various combinations of June, Fourth, 1989 and 6.4.

Big yellow duckThe great firewall is nothing if not thorough. Internet overlords are seeking to clamp down on all information about the crackdown. The growing use of Weibo and other social media has made it difficult for authorities to so.

Tiananmen Square means Gate of Heavenly Peace; big yellow duck refers to a giant sculpture currently occupying Hong Kong’s Victoria Harbour, which seems to have captured the public imagination. The phrase has been banned because the yellow ducks have been used to symbolise tanks in images referring to Tank Man, the individual who blocked a line of tanks in the street. Along with pictures of Lego Tank Man, the images have been doing the rounds on Weibo.

The Chinese government has never fully disclosed what happened on the night of June 3rd and the following day, and has labelled the protests a “counterrevolutionary riot”, refusing all efforts to reassess what happened. Activists in China took to social media to urge the public to wear black on the anniversary. There were a few black T-shirts in evidence, but it’s hard to say whether this was a political or a fashion statement.

Beijing is certainly a dirtier place than it was 24 years ago. I cycled to the square and had to wear a mask, as the air quality index read “heavily polluted” on my iPhone app.

The Tiananmen Square crackdown remains a taboo topic inside China, and most young people are barely aware that anything happened. One woman in her 20s told me how she only heard about the crackdown at university, because the brother of one her classmates had been involved.

“The consequences of the lack of information as a result of the censorship and disinformation about the Tiananmen Square massacre imposed by the government for almost 25 years are still felt today. Thanks to the effectiveness of the blackout, the vast majority of young Chinese still know nothing about this episode,” said Reporters Without Borders.

Powerful memoryBut for many who were there, or who were involved, it remains a powerful memory. Ding Zilin and her husband, Jiang Peikun, lost their son on June 4th. Ding is a founding member of the Tiananmen Mothers group, and she has spoken of a growing sense of despair about there being a meaningful assessment of what happened on that day.

Since writing the open letter, she and her husband have not been allowed to leave their apartment, even to mourn their son at the spot where he died. She wants President Xi Jinping to apologise for what happened. Bao Tong, a senior official who was jailed after the crackdown, told the South China Morning Post that suppressing the voices of dissent was doomed to fail. “If you cover the mouths of a hundred people, there could still be hundreds, thousands, tens of thousands of mouths still speaking,” he said.

China’s response to calls for a reassessment remains defiant. Foreign ministry spokesman Hong Lei told the US to “stop interfering in China’s affairs” when the US state department called for a full account of those who died, went missing or were jailed.

Cycling back from Tiananmen, I pass the spot where Tank Man stood, the lone protester carrying his shopping bags who dared to defy the tanks in the days before the crackdown. The photograph was taken from the Beijing Hotel – now a swanky hostelry – 100m or so from a gleaming new shopping mall.